The invention is directed to a method and to an apparatus for delivering components on a belt to an onserting machine.
In the automatic equipping (onserting) of printed circuit boards with surface-mountable components, what are referred to as SMD (surface mounted device) components, the SMD components are presented in the form of belted components, i.e, on belts. The form of delivery on a belt is particularly susceptible to automation since the components are already detached and the packaging in the belt assures far-reaching security against mistaken identity. In the individual delivery devices for belted components, the belts with the components are unwound from a belt reel and then supplied to a removal position for the components. In this removal position, the components are then picked up with the suction pipette of an onserting head and are then positioned in a predetermined onserting position on a printed circuit board. The cover foils of the belts that prevent the components from falling out of the component compartments of the belts are pulled off before the removal position is reached.
EP 0 589 276 discloses a delivery means for belted SMD components that comprises a movable covering of the component compartments in the removal region. This covering is moved synchronously with the belt in the unwinding direction of the belt until the front component compartment has reached the removal position. Subsequently, the covering is moved in the opposite direction for releasing the front component compartment. As a result of the movable covering, the SMD components are covered during transport in the removal region of a belt i.e. the components are prevented from jumping up or out of the component compartments.
It is felt to be a disadvantage, particularly given small components, that the components are fashioned smaller than the component compartments that accept them. Normally, the suction pipette anticipates the component in the middle of the component compartment in the removal position. Given large components (having an area of approximately 1 mm.sup.2), the precision of the positions of the components in the component compartments are not critical, since the lifting surface of the suction pipette is generally fashioned smaller than the component and therefore lands at least approximately in the middle of the surface of the component. Given small components (an area smaller than approximately 1 mm.sup.2), the lifting surface of the suction pipettes is partially larger than the components themselves. This so-called pipette projection then limits the packing density on the substrate to be equipped.
The foregoing gives rise to the concept of the "onserting shadow" or "equipping shadow". Given smaller components whose actual position in the component compartment deviates from the anticipated position in the middle of the component compartment, it can occur that the components are not correctly picked up and losses of time, among other things, are caused by mispositioned picking up new components, or damage can also occur when an incorrectly lifted component drops from the suction pipette into the automatic equipping unit during transport.